Project summary Exposure to environmental concentrations of pesticides and metals can cause neurobehavioral changes that influence survival of Pacific salmon. These neurological impacts that arise from central and peripheral nervous system deficits, including inhibition of peripheral olfactory function, may block the ability to detect predators and prey, alter reproductive timing, and interfere with homing to natal streams. The fish peripheral olfactory system is highly vulnerable to the toxic effects of dissolved contaminants due to its direct contact with the aquatic environment. Olfactory injury is now documented in other aquatic species exposed to environmental pollutants, suggesting far-reaching ecological ramifications of this phenomenon. The goal of our project is to understand the mechanisms of chemical-induced olfactory injury in Pacific salmon, and based upon our findings, generate biomarkers of olfactory injury to evaluate the ecological health and remediation outcomes at Superfund sites. Our studies will also use zebrafish, a well-defined genetic model, to better understand the mechanisms of olfactory injury that are relevant to salmon. In the current application, we will continue to integrate molecular, biochemical, physiological, and behavioral endpoints using model metal olfactory toxicants that are relevant to Superfund exposures. This novel approach allows a thorough understanding of mechanisms of chemical-induced olfactory injury in fish. In Aim 1, we will identify olfactory receptor neuron populations that are targets of cadmium (Cd) and address impaired olfactory signaling and neuron regeneration (neurogenesis) as mechanisms of Cd-mediated olfactory injury. In Aim 2, we will investigate transcriptional and post-transcriptional control of olfaction during metal exposures. We will identify functionally-important olfactory microRNAs (miRNAs) and their gene targets that are important regulators of metal-induced olfactory injury. In Aim 3, we will develop olfactory biomarkers generated from our work for field studies at Superfund sites. We will verify and test glutathione S-transferase (GST) isoforms as biomarkers of olfactory injury, and carboxylesterase- organophosphate protein adducts as markers of organophosphate exposures. We will use transgenic zebrafish to evaluate other common, but untested, Superfund metals as olfactory toxicants. We will incorporate our olfactory molecular biomarkers within a multiplex platform to evaluate remediation outcomes in the lower Duwamish waterway, a regional Superfund site at various stages of remediation. We have assembled a strong team of collaborators for this project whose interactions are described in the proposal. We have endeavored to be responsive to SRP objectives by using mechanistic approaches to address health hazards and remediation outcomes at Superfund sites in collaboration with EPA partners involved in Superfund site assessment.